Late Pleistocene glaciations on the sub-Antarctic Kerguelen Archipelago: new evidence from 36Cl CRE dating and comparison with other southern mid-latitude glacier records

Abstract

Previous paleo-glacial studies on Kerguelen showed a singular pattern of Holocene glacier evolution on this archipelago in comparison with other southern mid-latitude glacier records. In this study, we aim to test this singularity on a longer timescale, based on 26 new in situ-produced 36Cl ages from pre-Holocene glacio-geomorphic features. Samples from moraine boulders and glacially polished bedrock were extracted at six different sites, located near the Port-aux-Français scientific station (PAF site), on Longue Island, Australia Island, on the Port-Jeanne d’Arc Peninsula (PJDA site), on the Gallieni Peninsula at Baie Larose (BLR site) and the McMurdo Island. The moraine ages indicate that glacier culminations occurred during Marine Isotopic Stage 3 (MIS 3) at 42.2 ± 4.9 ka on the PAF site, and during the global Last Glacial Maximum (gLGM) at 21.5 ± 3.2 ka on the PJDA site and at 21.4 ± 3.7 ka and 19.4 ± 2.6 on Baie Larose site. This is the first time that Late Pleistocene glacier culminations are evidenced on Kerguelen by direct moraine dating, thus allowing comparison with other moraine records from the southern mid-latitudes. While it remains speculative whether or not the MIS 3 glacial maximum at ⁓42.2 ka is in phase with other glaciers at this latitude (due to high age uncertainties), the gLGM glacial maximum is synchronous with that in other southern mid-latitude regions. 36Cl CRE ages of glacially polished bedrock surfaces sampled in different locations of the archipelago vary from ⁓39 ka to ⁓19 ka. We interpret these results as reflecting periods of deglaciation that occurred in between the two glacier culminations and right after the gLGM on Kerguelen. These ages also suggest that some places of the archipelago were free of ice at least since ⁓ 39 ka. The presence of a MIS 3 moraine at PAF site that has not been obliterated by a gLGM advance suggests that the ⁓ 42.2 ka glacier extent was at least as large as gLGM glacial maxima on the archipelago. The glacier culmination during MIS 3 being larger than that during the gLGM on the Kerguelen Archipelago matches observations in other southern mid-latitude regions. Late Pleistocene glacier culminations on Kerguelen may have been in phase with cold temperatures recorded in SST records, which suggest a cooling around Kerguelen. However, climate drivers responsible for the larger MIS 3 glacier culmination on Kerguelen still remain unclear even if we hypothesize that changes in precipitation may have superimposed on temperature changes.